There has been proposed a technique for twisting the body trunk of a legged mobile robot, which travels (walks) by alternately moving forward its right and left legs extending downward from its body, to increase a stride thereof so as to permit fast walking (refer to, for example, paragraph 0077 and FIG. 24 to FIG. 28 of Japanese Patent Laid-Open Publication No. 2004-202652).
However, as the walking velocity increases, the moment generated in the direction in which the body trunk of the robot is twisted increases. This may lead to lateral wobble in the direction in which the robot is advancing and further cause the robot to spin with resultant instability in a walking motion thereof. In particular, a running motion of the robot, which includes a floating period (=a period in which all legs are in the air), is very likely to become unstable when a leg lands onto a floor.
Accordingly, an object of the present invention is to provide a legged mobile robot capable of maintaining stable motions involved in travel, and a control program for the same.